High-availability (HA) clusters (also known as failover clusters) are groups of computers and/or computer components that support server applications and/or provide storage that can be reliably utilized with minimum down-time. HA clusters may include and utilize redundant computers and/or redundant components that provide continued (i.e., uninterrupted) service when computers and/or components fail. Without clustering, if a computer or component crashes, the application or storage provided by that computer or component will be unavailable until the crashed computer or component is fixed. The term “port failover” (or simply, “failover”) or “multipathing” may refer to the switching from a failing computer/component to a redundant or standby computer/component upon the failure or abnormal termination of the previously active computer/component. Additionally, redundant computers/components may result in increased bandwidth as experienced by host computing devices that connect to the HA cluster.
Small Computer System Interface (SCSI) is a set of standards for physically connecting and transferring data between computers and peripheral devices. The SCSI standards define commands, protocols and electrical and optical interfaces. SCSI is most commonly used for hard disks and tape drives, but it can connect a wide range of other devices, including scanners and CD drives. Serial Attached SCSI (SAS) is a serial communication protocol that is used to move data to and from computers and peripherals, for example, storage devices such as hard drives and tape drives. SAS was designed to replace the older parallel SCSI bus technology. SAS, like parallel SCSI, uses the standard SCSI command set.